Offline Sync is the worst, no one should ever use it, but if someone does here is some information to potentially mitigate your inevitable headaches and nightmares.
Disable Offline Sync (XP)
Double click on My Computer
Click Tools and then click Folder Options
Click on the Offline Files tab
Uncheck the Enable Offline Files check box
Files have dissapeared
When you turn off offline sync files that you thought were on the server may disappear and suddenly you will not have access to the folders/files you wanted. This is because those folders/files were never synced to the server and offline sync may have notified you of this failure to sync but the notification is hidden and easily ignored. If this happens you can either turn offline sync back on to re-access your folders or you can recover the files from your local cache.
Recover Offline sync files from local cache
Navigate to C:\Windows\CSC
The CSC folder will contain a cache of all offline sync files/folders provided you have allocated enough hard drive space to store the files in cache.
Change Offline Sync Partition Drive letter and folder
This can be done through a Directory Junction which can redirect to a new location of offline files.
The Offline Files are stored in the folder %SystemRoot%\CSC (which usually is C:\Windows\CSC or a different drive letter in place of C).
Create a folder on a partition with large space and give it an informative name, say, D:\Offline Folders as a suggestion.
Turn off offline sync and reboot the computer
rename the %SystemRoot%\CSC folder to something else to create a backup of it
Create a symbolic link to the new location for the CSC folder: mklink /J%SystemRoot%\CSC <new-folder-path> for example: mklink /J C:\Windows\CSC "D:\Offline Files"
Now enable offline sync and restart the computer
Now, whatever is meant for location %SystemRoot%\CSC gets directed to the new location.
Disable Offline Sync (XP)
Files have dissapeared
When you turn off offline sync files that you thought were on the server may disappear and suddenly you will not have access to the folders/files you wanted. This is because those folders/files were never synced to the server and offline sync may have notified you of this failure to sync but the notification is hidden and easily ignored. If this happens you can either turn offline sync back on to re-access your folders or you can recover the files from your local cache.Recover Offline sync files from local cache
Change Offline Sync Partition Drive letter and folder
This can be done through a Directory Junction which can redirect to a new location of offline files.The Offline Files are stored in the folder %SystemRoot%\CSC (which usually is C:\Windows\CSC or a different drive letter in place of C).
Now, whatever is meant for location %SystemRoot%\CSC gets directed to the new location.